Nonlinear temperature variation of magnetic viscosity in nanoscale FeOOH particles

Magnetic relaxation and correlating effective magnetic moment with particle size distribution in maghemite nanoparticles

“…The determination of ƒ o and T o from this variation is discussed below. [20] and ferrihydrite [30,31].…”

Normalization factors for magnetic relaxation of small-particle systems in a nonzero magnetic field

“…When this is the case, non-normalization could give place to a spurious thermal dependence. In the case of relaxation experiments performed in an applied magnetic field, there exists a certain controversy in the literature about the nature of the normalization: Either no normalization factors are used at all 8,24,25 or the FC magnetization value, corresponding to the field at which the experiment is performed, 10 is used.…”

Thermally assisted resonant quantum tunneling of magnetization in Fe8 clusters

“…Therefore, by fitting T p obtained from Fig. 2 for different frequencies to ln fϭln(f 0 /2 )Ϫ(U/k B T p ), f 0 ϭ1.54ϫ10 8 Hz, and U/k B ϭ26.94 K were obtained. The energy barrier U/k B ϭ26.72 K and the attempt frequency f 0 ϭ1.39ϫ10 8 Hz have also been obtained from the temperature-dependent susceptibility measured on the powder sample, consistent with the values obtained on the oriented sample.…”

“…7,8 The resonant tunneling of spins ͑or magnetization͒ is said to be thermally assisted, that is, the measured magnetization change ͑or susceptibility͒ caused by the resonant tunneling effect is governed not only by the tunneling rate of the dominant spin level͑s͒ but also by the thermal population of the very spin level͑s͒ simultaneously. It was found that the tunneling effect can be tuned by temperature and applied magnetic field, which resulted in the observation of some characteristic features ͓e.g., the jumps equally spaced in magnetization data M (H) [1][2][3][4] and peaks in the real part of susceptibility Ј(H)].…”